1. Field of the Invention
The present invention relates to a gene, especially a cloned gene coding for a interleukin-2 polypeptide, recombinant DNA carrying the gene, a living cell line possessing the recombinant DNA and a method for producing interleukin-2 using the cell line.
2. Brief Description of the Prior Art
Interleukin 2 (hereinafter referred to as "IL-2"), formerly referred to as T cell growth factor, is a soluble protein (generally known as "lymphokine"), and is produced from T cells activated with a lectin or an antigen (Morgan. D. A., et al., Science, 193, 1007-1008 (1976), Gillis, S. et al, J. Immunol., 120, 2027-2033 (1978). Interleukin 2 (IL-2) is capable of modulating lymphocyte reactivity and promoting the in vitro long-term culture of antigen specific effector T-lymphocytes (Gillis. S. et al., Nature 268, 154-156 (1977)). IL-2 is also known to manifest other relevant biological activities such as enhancement of thymocyte mitogenesis (Chen, B. M. et al., Cell. Immunol., 22, 211-224, (1977), Shaw, J. et al., J. Immunol. 120, 1967-1973, (1978)), induction of cytotoxic T cell reactivity (Wagner, H. et al., Nature, 284, 278-280, (1980)) and anti-SRBC plaque forming cell responses (Gillis, S. et al., J. Exp. Med., 149, 1960-1968, (1979)) in cultures of nude mouse spleen cells. Accordingly, this lymphocyte regulatory substance is useful in potentiating humoral and cellular immune responses and in restoring immune deficient state to a normal humoral and cellular immune state. These identified immunological activities of IL-2 strongly indicate that IL-2 is useful for medical immunotherapy against immunological disorders including neoplastic diseases, bacterial or viral infections, immune deficient diseases, autoimmune diseases etc.(Papermaster, B. et al., Adv. Immunopharm., 507, (1980)). Like interferons, IL-2 has been shown to augment natural killer cell activity, suggesting a potential use in the treatment of neoplastic diseases. Furthermore, IL-2 enables the maintenance of cultures of functional monoclonal T cells and hence appears to play a key role in the studying of the molecular nature of T cell differentiation, and of the mechanism of differentiated T cell functions as well as the mechanism of T cell antigen receptors. It is also useful for producing, by long term culturing of monoclonal T cell, many other T cell derived lymphokines, which are useful in a wide range of fields. In addition, IL-2 production and the response of lymphocytes to IL-2 can be important parameters of immunological functions which are useful in the clinical diagnosis of aberrant immunity.
IL-2 has been produced in the prior art by stimulating mouse, rat or human lymphocytes with a mitogen (Gillis. S. et al., Nature, 268, 154-156, 1977, Farrar, J. et al., J. Immunol., 121, 1353-1360, (1978), Gillis, S. et al., J. Immunol., 120, 2027-2033, 1978,)). By stimulating human peripheral blood mononuclear lymphocytes with a mitogen (Gillis. S. et al., J. Immunol., 124, 1954-1962, (1980)). Gillis et al. reported the preparation of murine IL-2 from murine T cell lymphoma cell line (Gillis. S. et al, J. Immunol., 125, 2570-2578 (1980)) and the preparation of human IL-2 from a human leukemia cell line (Gillis, S. et al., J. Exp. Med., 152, 1709-1719, (1980)).
The above noted articles by Gillis et. al. discuss the method of producing human IL-2 from mitogen-stimulated human T cell leukemia cell line by cell culture methods. However, such a technique results in undesirably low concentrations of human IL-2, and necessitates complex purification procedures to obtain even small amounts of IL-2 from a huge volumes of culture media. Moreover, since the human T cell leukemia cell lines produce trace amounts of many other biologically active substances which are analogous to human IL-2, significant difficulties are encountered in isolating IL-2 from these other immunologically active molecules, or in isolating IL-2 from the occasionally present toxic lectins.
As an alternative approach it would seem to be desirable to use recombinant DNA (DNA is an abbreviation for deoxyribonucleic acid) techniques as are used in the production of other biologically active human proteins, such as interferons, (Gray, P. W. et al., Nature, 295, 503-508, (1981), Nagata, S., et. al., Nature, 284, 316-320, (1980), Taniguchi, T. et. al., Gene, 10, 11-15, (1980)) to produce IL-2. However to date, attempts at the production of IL-2, by recombinant DNA techniques have not been successful. For instance, it was reported in "NIKKEI BIOTECHNOLOGY (Japan), No. 19, Jul. 5, 1982 that attempts to construct IL-2-producing organisms by recombinant DNA were unsuccessful, probably due to the fact that the gene coding for IL-2 polypeptide had not yet been cloned.
A need therefore, continues to exist for a cloned gene, coded for interleukin-2, and for DNA produced recombinantly which carries the gene. A need also continues to exist for a living cell line which possesses the recombinantly produced DNA, and for a method of producing interleukin-2 using the cell line.